PROJECT SUMMARY The Clinical Core C, based at the University of Maryland School of Medicine, will provide specimens and data acquisition services to the Eco-Pathogenomics of Sexually Transmitted Infections (EPSTI) Program. The Core will recruit new participants to the Sexually Transmitted Infection Network Groups (STING) study. STING is designed as networks of sexual contacts. Couples discordant for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (GC) will be present in the networks and will allow for detailed analysis of protective and susceptibility features of the host, pathogen(s) and genital microbiome in Projects 1-3. Wave 1 recruitment will include genital CT screen positives (both men and women) and also women with pelvic inflammatory disease (PID). Each participant will be asked to report recent (past 60 days) sexual partners who will in turn be approached for participation in Wave 2. Each participant will be screened for CT/GC, and will also report their sexual partners for another wave of recruitment (Wave 3). The network capture will be repeated annually for 4 years for a maximum of 560 people recruited. Over the duration of the Program, the specific aims of Core C are to 1) provide biological specimens and behavioral data to EPSTI Projects 1-3, and 2) build multiple networks of sexual partners for sample collection and analysis. Collection of whole blood and vaginal lavage will be used in Project 1 to determine the effects of human genetic variations on disease transmission and severity. Serum, urethral, and endocervical swabs will be collected for Genomics Core B and Project 2 to assist in the determination of CT and/or GC biomarkers as well as CT antibody response related to disease severity and ascending infections. Collection of vaginal, urethral, and endocervical specimens will be performed to assist Project 3 in the evaluation of molecular interactions of the host/pathogens/microbiome at the cervical epithelium in discordant versus concordant infected couples and those with and without co- infections. Demographic and extensive behavioral information will be collected from all participants to provide context for the biologic information that is ascertained. The Core will be co-directed by two gynecologists with expertise in sexually transmitted infection research (Mishka Terplan, MD, MPH and Katrina Mark, MD). The co- directors will be responsible for communicating with key personnel of the Genomics Core B and project PIs to facilitate data sharing, analysis and dissemination in coordination with the Program Manager. Sexual networks are central to the spread of STIs. Both individual-level attributes (behavioral, genetic and biological) as well as attributes of the individual's sexual partner(s) (Project 1) are critical to understanding the spread of infection and the evolution of the pathogens through sexual transmission (Project 3). The sexual network recruitment that we propose will inform our studies on CT/GC acquisition, re-infection, and co-infection.